4. Negative serum pregnancy test for females of child-bearing potential. Patients must agree to one of the following birth control methods: an oral contraceptive agent, an intrauterine device (IUD), an implantable contraceptive (e.g., Norplant), or an injectable contraceptive (e.g., Depo Provera) for at least 1 month prior to entering the study and will continue its use through at least 30 days after the last dose of study medication or a barrier method of contraception, e.g., condom and/or diaphragm with spermicide while participating in the study through at least 30 days after the last dose of study medication or abstinence.